The following U.S. Patents are representative of the most relevant prior art known to the applicant at the time of the filing of this application.
______________________________________ U.S. Pat. Nos. ______________________________________ 933,603 Wagg September 7, 1909 2,369,639 Ball et al. February 20, 1945 2,453,748 Fisher et al. November 16, 1948 2,887,276 Minarik May 19, 1959 4,351,486 Schmoller et al. September 28, 1982 ______________________________________
The conventional pulpstone is usually made by assembling a plurality of abrasive segments that are then filled with a concrete core whereby to form an abrasive periphery integral with a central core made of concrete, or in some instances it has been proposed to assemble such segments on the periphery of another form of a rigid body like a cylindrical metal annulus. The segments are frequently provided with integral studs extending radially inwardly toward the center of the pulpstone, which segments are assembled together with a concrete core by means of these studs being bolted to the reinforcing cage of the concrete core, the studs subsequently becoming permanently bonded and sealed within the center core.
The patent to Fisher et al. is of general interest only in showing an abrasive grinding wheel for the surface finishing of glass plates wherein the grinding wheel means is constructed with abrasive segments bolted to a circular supporting ring means. The grinding wheel of this disclosure utilizes the exposed ends of the segments for grinding the glass sheet being polished as distinguished from the periphery of the wheel as with a pulpstone used for grinding logs to make a wood pulp. As the segments of the glass plate grinding means wear down, the successive rings that support the segments may be removed to provide a continuing support for the remaining portions of the abrasive segments forming the wheel.
The remaining patents cited above all show grinding wheels for use in making wood pulp. Wagg and Minarik each show a bolting arrangement for attaching a plurality of abrasive elements to a centrally disposed metal cylinder or ring. The Wagg patent teaches the use of a molten filler flowed into place between the segments and the mounting means therefore to preclude any movement of the segments relative to it's metal support ring when the wheel is in use. The Minarik disclosure uses an eye-bolt with each segment, the eye-bolt being carried on a crossrod that passes through the center of each of the individual segments of a pulpstone to fasten the individual segments to the surface of a cylindrical cast iron drum. In this construction the individual segments are mounted on the drum with spaces between all sides of the individual segments to make passages available for the circulation of a fluid from the cylinder through the spaces to the grinding surface of the stone to assist in the grinding process.
Ball et al. provides a wheel wherein a unitary solid annulus constitutes the grinding element of a pulpstone, as distinguished from a pulpstone fabricated with a plurality of individual segments assembled together on the periphery of the grinding stone to form the grinding surface of the pulpstone structure. This Ball et al. disclosure provides for the attachment of the annulus to a metal ring positioned concentrically within the annulus and threaded spokes that have one end integrally attached to the respective side walls of the annulus that are used to tension the annulus around the metal ring to prestress the abrasive ring against the stresses produced by the grinding process. The central opening in the Ball et al. annulus is filled with concrete after the annulus has been mounted on the metal ring and the nuts 11 by which the tension in each of the respective spokes is adjusted then become permanently sealed within the concrete core.
Schmoller et al. disclose several systems for mounting abrasive segments on the periphery of pulpstones. In FIGS. 1-5 a very general disclosure sets forth a bolting arrangement for supporting such segments on a concrete core and in FIGS. 6-11 the segments are shown mounted on a steel ring or cylinder. In each instance the segments are each provided with nut means situated within the segments that are simply threaded onto bolts extending outwardly from a support cylinder to hold the several segments onto their support means, there being no detailed discussion of the particulars of the bolting system except as the bolt structures are modified to promote the circulation of water to the surface of the pulpstones through the segments which are made somewhat porous or are spaced apart to permit the water to flow outwardly to the surface of the pulpstone.